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The Demon Core
The following is an article from the newest volume of the Bathroom Reader series, Uncle John’s 24-Karat Bathroom Reader.
The real-life story of a small ball of plutonium, the people it killed, and the researchers who blew it up.
THE BOMB
On the evening of Tuesday, August 21, 1945, American physicist Harry Daghlian was working at the U.S. government’s ultra-secret Los Alamos National Laboratory in New Mexico. He was performing a very delicate experiment: Daghlian was placing brick-shaped pieces of metal around a chunk of plutonium, the highly unstable fuel used in most nuclear bombs. And he was making it more unstable with every brick he placed around it.
Daghlin (pronounced “DAHL-ee-an”) was part of the government’s Manhattan Project, which since 1942 had worked to develop the world’s first atomic bombs. And they succeeded: Just a few weeks before Daghlian’s experiment, two atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki. The bombs had killed at least 100,000 people immediately, and many tens of thousands more in the days that followed. Less than a week after those bombings Japan surrendered to Allied forces, ending World War II.
For Daghlian and his fellow scientists, that meant there was much more work to do.
NEW AND IMPROVED
The United States was the only country in the world with nuclear weapons at the time, but the government knew that wouldn’t be the case for long. If America was going to survive in a world with nuclear-armed enemies, it was reasoned, the nation was going to have to keep producing these weapons, and make them even more effective. This was precisely the reason that Daghlian was doing the particular work he was doing that night at Los Alamos.
Harry Daghlian was just 24 years old. He’d been brought into the Manhattan Project in 1943, while he was still a physics student -and an exceptionally brilliant one- at Indiana’s Purdue University. He had helped in the development of the bombs used in Japan, which, their devastating effects aside, were actually not very good nuclear bombs. They were, after all, only the second and third ever exploded (one test bomb had been detonated in New Mexico just three weeks before the two in Japan).
One of the chief issues for the scientists was determining how to take full advantage of the bomb’s nuclear fuel. Amazingly, both bombs used in the attack on Japan used only tiny fractions of their fuel to produce their explosions. (Imagine if they had used it all.) And using a bomb’s fuel efficiently is all about the neutrons.
THE NEUTRON DANCE
The most common type of fuel used in nuclear weapons is a type of plutonium known as plutonium-239, or Pu-239.
* Pu-239 is naturally radioactive, meaning that its atoms naturally emit particles from their nuclei. Some of those particles are neutrons. (This is known as neutron radiation.) Neutrons are very large, as atomic particles go -so large that if a neutron emitted from one atom happens to strike another atom, it can actually “break” it, and cause the second atoms to eject some of its own neutrons. (This is the “split” in “splitting the atom,”and scientifically, it’s known as fission.)
* This process happens normally very slowly, because most of the radiating neutrons just fly off. The whole idea behind nuclear weapons is to contain those neutrons within the plutonium, thereby speeding up the splitting process -with neutrons smashing atoms, causing more and more neutrons to be emitted, smashing more and more atoms- until it is completely out of control.
* The numbers involved in this chain reaction are almost too big to fathom: In a nuclear bomb explosion, atoms of the nuclear fuel are split by neutrons trillions and trillions of times …in hundreds of billionths of a second. Because each split of each atom releases energy, the combined splitting of trillions of atoms in such an impossibly short amount of time releases an absolutely phenomenal amount of energy -hence the power of atomic bombs.
And that small box that Harry Daghlian was building that night in August 1945 was all about containing the neutrons.
more …
In 1945, physicist Harry Daghlian was working on a 6.2 kg (14 lb) spherical mass of plutonium at the Los Alamos laboratory. He was stacking bricks of tungsten carbide around the plutonium core when he noticed a nearby neutron counter signaling that the addition of the final brick would make the assembly supercritical. Daghlian immediately withdrew his hand ... and the brick slipped onto the center of the plutonium core and the assembly went critical. Daghlian was able to dissemble the bricks (the core didn't explode), but he died from radiation poisoning 28 days later.
Nine months later, physicist Louis Slotin, an expert in triggering devices, and seven other scientists gathered in the laboratory to perform a dangerous experiment he called "tickling the dragon's tail." The experiment involved creating the beginning steps of a nuclear fission reactor by placing two half-spheres of beryllium around the plutonium core. The trick was to keep the beryllium from touching the plutonium core, which Slotin had done many times before.
But on that day, Slotin decided to use a screwdriver instead of shims, and his hand slipped and the beryllium hemisphere touched the plutonium core, which instantly went critical. Slotin realized his mistake, and used his hand to lift the beryllium just a fraction of a second later ... but that was enough to give him a lethal dose of radiation. The other scientists saw a "blue glow" of air ionization and felt a "heat wave" - they were saved from immediate death (though later 3 of them died from side effects of radiation years later). Slotin, on the other hand, died 9 days later.
Both of Daghlian and Slotin's accidents were on Tuesday the 21st, both used the same plutonium core, and both died in the same room at the same hospital. The plutonium core was later named the "Demon Core" and was put to use in the Able test of the Operation Crossroads nuclear weapon test at the Bikini Atoll in the summer of 1946.
The Able test of Operation Crossroads, July 1, 1946.
Photo: Office
of History & Heritage Resources
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